From Opus

Alternative name: Great Northern Diver; Great Northern Loon

Photo by BigSkyBirds
Missouri River, Great Falls, Montana, USA, April 2005

Gavia immer

[edit] Identification

Length 65-91cm Wingspan 137cm
The most numerous loon in North America and a familiar bird on its breeding grounds.

Winter plumage
Photo by blubird
Bodega Bay, California, January 2011

[edit] Adult breeding

• Black above with bold white chequer-spots
• White below
• Head black with collar of short vertical white stripes, broadest on hindneck
• Half-necklace of white spots below chin

[edit] Adult non-breeding

• Blackish-grey above and white below
• Lacks sharp contrast seen in Black-throated Diver (G. arctica)
• Head and neck usually darker than back
• Shows indistinct half-collar at base of hindneck
• Usually lacks white flank patch.

Some show whitish bills but culmen is always dark.

[edit] Similar Species

Best distinguished from smaller species by heavy build and bill and from the Yellow-billed Diver (G. adamsii) by straighter, usually darker bill, held horizontally.

[edit] Distribution

Photo by Glen Tepke
Monterey Bay, California, USA, October 2007

[edit] Breeding

Common and widespread across North America breeding from Alaska south to northern Washington and east to the Great Lakes and New England. Absent from north-central Arctic Canada and south-central Canada. Also breeds in Greenland and Iceland. Possibly breeds regularly on Bear Island and has bred in Scotland.

[edit] Non-breeding

Winters in North America from the Aleutians south to northern Mexico in the west and from Newfoundland to the Gulf Coast in the east. European birds winter from Iceland and northern Norway south to northwest France with vagrants recorded on the Azores, on the Mediterranean coast of North Africa and in Ukraine.

[edit] Taxonomy

This is a monotypic species^[1], but birds from western Canada are sometimes separated as race elasson.

[edit] Habitat

Breeds on medium-large, deep lakes in tundra and forest areas.

Winters at sea in bays and estuaries, sometimes large inland waters.

[edit] Behaviour

[edit] Breeding

Breeds late-May or early June to September. Nests beside water often on an island or spit, a shallow scrape or more rarely a substantial mound of vegetation built in shallow water in reedbeds. Eggs: 2 (1 in replacement clutch), olive-brown, sometimes more greenish with sparse black blotches (90 x 57mm). Incubated by both sexes for 29-30 days. Young tended by both sexes, feed themselves at 40 days and fly at about 72 days

[edit] Diet

Fish, also molluscs and crustaceans caught during 60-120 second dives.

[edit] Vocalisation

Familiar loud wailing and yodelling calls during the breeding season.

[edit] References

1. Clements, JF. 2010. The Clements Checklist of Birds of the World. 6th ed., with updates to December 2010. Ithaca: Cornell Univ. Press. ISBN 978-0801445019. Spreadsheet available at http://www.birds.cornell.edu/clementschecklist/Clements%206.5.xls/view

• List of references

[edit] External Links

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